This is a prospective, experimental study designed to understand the role that social stress plays in disease progress in AIDS. Eighteen rhesus macaques were inoculated with SIVMAC251 and 18 served as uninoculated controls. Half of each group experience stable social conditions, and half experience unstable social conditions. Animals are placed together daily for two hour periods in their respective social groups. Progress to date has reflected mostly pre-inoculation manipulations focusing on individual differences in social, emotional, neuroendocrine, and immunological functioning that may predict disease course. Progress in the post-inoculation phase has centered on characterizing group (stable vs. Unstable) differences in the initial stages of SIV infection. Preliminary analyses suggest that social instability is associated with poorer control of the infection, and that, within stable groups, greater affiliation is associated with better control of the infection.